1. Field of the Invention
The present invention relates to a balloon catheter and a method of deploying stents, and more particularly, to a balloon catheter delivery system for delivering and deploying stents within a tubular organ of the body and a method of deploying stents employing the balloon catheter delivery system.
2. Description of the Related Art
Conventionally, expandable devices, called stents, are used to maintain the inner diameter of a body lumen such as an artery. Although stents are most commonly used after angioplasty, to maintain vascular patency and help in the prevention of restenosis, stents may also be used for repair of aneurysms, stabilization of interior vessel tubes such as bronchial tubes, retention of emboli and plaque, and prevention of vessel collapse. The stents are placed at a desired location within a body lumen through a guide catheter or similar device and are expanded, by various known methods, within the lumen until they are opposed to the walls of the lumen at a preferred diameter.
According to one conventional procedure for installation of stents, a stent is positioned over an inflatable portion of a catheter, such as an angioplasty catheter balloon, which is inserted into a body lumen to a position where it is desired to place the stent. Fluoroscopy, and/or other conventional techniques may be utilized to ensure that the catheter and the stent are delivered to the desired location. The stent is then expanded radially outward by inflating the expandable portion of the balloon catheter until the stent is in contact with the walls of the lumen. After the desired expansion has been accomplished, the balloon is collapsed, or deflated, and the balloon catheter is removed from the lumen.
A substantial difficulty with the conventional method of deploying a stent is the tendency for movement of the stent on the balloon. The movement of the stent on the balloon provides a potential for embolism, non-uniform expansion of the stent and the inability to retract the stent if necessary. Proposed solutions to this problem include providing a tubular protective sheath over the stent to secure the stent in place. Once the stent is in the proper position, the sheath is removed to expose the stent. The use of a sheath is disclosed in U.S. Pat. Nos. 5,158,548 and 5,102,417. Protective sheaths have drawbacks in that the sheath is bulky, the stent is not secured to the balloon under the sheath, and once the sheath is deployed the stent is not secure for further positioning. Therefore, once the sheath is removed, the stent cannot be retracted from the body on the uninflated balloon.
Another proposed solution to the problem of movement of the stent is the use of machine crimping to fix the stent on the balloon. The crimping of portions of a stent provides friction between the stent and the balloon which prevents the stent from sliding off the balloon. The use of machine crimping is discussed in U.S. Pat. No. 4,969,458. This method, however, may tear or puncture the balloon and will tend to make the stent stiff and difficult to insert.
A third proposed solution to the problem of movement of the stent is the use of an adhesive to bond the stent to the balloon. However, the use of adhesive is relatively unreliable and may create problems due to loose particles of adhesive which contaminate the surgical site. Other stent insertion catheters having means for retaining the stents on the catheters prior to deployment are disclosed in U.S. Pat. Nos. 4,969,890 and 5,102,417.